With an absorbtion system, it has to be as level as possible in order for the coolant used to boil off. An air blockage is possible, moving the camper up and down with the front jack may break it lose or you can hook up the camper and go for a short drive.
Another possibility is a leak in the system. Look for any greenish color around the fittings and or joints, that will indicate a leak. Had this happen to me back in 07 with a PUP I had. Fridge worked great for three campouts and on the forth, the fridge would not cool at all, had a leak at a joint indicated by a greenish color at a joint.
Then there's always the thermostat check, have turned it up for whatever reason and forgot to turn it down when I used it again. Hope this and all comments from others help. Let us know what you find. Good Luck
2016 Forest River Surveyor 201RBS
2014 Chevy Silverado 1500 4.3L